Adjustable drill guide and pilot



Feb. 15, 1949. l.. F. BLATT ADJUSTABLE DRILL GUIDE AND PILOT Filed Maron s1, 1947 JNVENTOR.

LELAND F. BLATT 1WA ATTORNEY Patented Feb. ,15, 1949 UNITED STATES PATENT OFFICE 2,461,716 ADJUSTABLE DRILL GUIDE AND PILOT Leland F. Blatt, Detroit, Mich.

Application March 31, 1947, serial No. 738,355

1 Claim.

This invention relates to guides for drill bits, andV particularly guides which kalso exercise a pilot function.

It is common inthe use of drills, both of the press and portable type., t provide a tubular guide projecting lfrom the drill, to receiv'e a bit in proximity to the work and resist flexing and weaving of the bit, and it has further been proposed to form a pilot extremity on such a guide and to insert such extremity in an opening of a drill plate, set against the work, to predetermine the location of drilled holes in the work. While such constructions are desirable and are a factor in reducing breakage of bits, they fail to establish a maximum safeguard against damage to bits, since they do not sufliciently regulate the effective stroke of a bit according to the requirements of any certain job. When a piece of work is to be drilled with a certain pattern of through holes, there is usually used a backing vplate or support underlying the work as well as a drill plate against the exposed face of the work. Unless the effective stroke is nicely regulated, the bit will encounter the support upon breaking through the work, this tending to dull the bit, and quite commonly the bit embeds itself in the support and is broken, unless quite carefully retracted.

The object of the invention is to provide a drill guide that may be adjusted to accurately predetermine the effective stroke of the drill bit, so that the latter may be safeguarded from contact with any support underlying the work.

Another object is to provide an accurately adl justable drill guide suited for a piloting engagement in a pattern-forming drill plate disposed against the work.

Another object is to adapt a drill guide to occupy an abutting relation to a piece ofwork while a bit positioned by said guide enters the work and to provide in a novel manner for restraint of the guide from rotation.

These and various other objects are attained by the construction hereinafter described and illustrated in the accompanying drawing, where- Fig. 1 is a side elevational view of my improved guide and pilot.

Fig. 2 is an axial sectional View of the same, as applied to a drill, and in operative relation to a piece of work.

Fig. 3 is a cross sectional view taken on the line 3-3 of Fig. 2.

Fig. 4 is a perspective view of a key used to interlock certain parts of the construction.

2 In these Views, the reference character I designates a drill frame, 2 a shaft journaled in said frame and usually driven by an electric motor (not shown) and 3 an ordinary chuck carried by the shaft 2 for gripping and driving a bit 4. My

improved pilot and guide comprises a split collar 5 adapted to be clamped on the frame I' by a screw 6, an arm l integrally projecting from said collar alongside the chuck, a, head 8 on the front 0 end of the arm l, yprojecting across the front end of the chuck, and an elongated tubular member 9 rigidly forwardly projecting from the head 8 and coaxial with the bit 4. The head 8 has an opening I0 accommodating the bit and affording it clearance. Slidable in the member 9 is the rear portion of a tubular guide II for the bit, and a spring I2 housed within the member 9 reacts between the head 8 and said guide to urge the guide forwardly, to a position in which its front end adjoins the front end of the bit. A key I3 set into an elongated recess exteriorly formed in the member 9 has an inturned forward end I 3a projecting into a slot I4 longitudinally extending in the guide Il. This key limits response of the guide to the spring I2 and also restrains the guide from rotation.

At a suitable distance from its ends, the guide I'I is formed with an exterior annular shoulder I 5 for engaging a nut I 6 threaded on the member '9, the nut having an interior annular ange I6' at its front end for contact by said shoulder. By suitably adjusting the nut I 6, the retraction afforded the guide II may be regulated. A locknut II on the member 9 is adapted to rmly secure the nut I6 in any position of adjustment.

As is apparent from Fig. 2, the nut I6 retains the key I3 in its use position.

At I'B is shown a sheet of metal or other material requiring a plurality of drilled holes and a predetermined pattern for such holes is established by openings I9 in a drill plate 20 held in any desired manner against the sheet I8. Against the opposite face of said sheet is set a backing plate or other support 2| and it is usual to form such support with recesses 22 or other clearance openings for the drill bit.

Preliminary to use of a drill equipped with the described guide for the bit. the nut I6 is adjusted to afford the bit a travel adequate to cut through the work without excess motion. The forward end of the guide is then inserted in one of the openings I9 of the drill plate. and the bit is fed through the work by advancing the frame I and chuck 3. the guide II abuttingr the work and acting as a pilot for the drill. Immediately after a hole has beendrilled, the nut I6 encounters the shoulder l5, preventing further advance of the bit. The latter consequently cannot strike or penetrate the work support 2 l' and can neither damage such support nor be damaged thereby. Pattern drilling, such as has been described, is usually performed by persons having Very little skill or mechanical ability, and the result heretofore has been a considerable breakage of bits due to driving the drill too deep. By 'permitting the stroke to be accurately regulated, the present invention eliminates damaging or breaking drills due to such unskilled workmanship.

What I claim is: ,Y

In a drill guide, the combination with a drilling tool and a bit driven by such tool, of an'attachment comprising an elongated tubular` guide member in which the bit is rotatable, such member having a work-engaging extremity, -a support for said guide member elongated axially of said tool and having a rear end portion fixed on a non-rotating portion of said tool and having a tubular front end portion in which said guide member is slidable, a spring reacting between the support and tubular guide member to urge the guide member toward the point of the bit, a stop element exteriorly carried by said guide member,

and a companion stop element carried by said support adjustable to and from the stop element on the guide member to selectively limit the effective stroke of the bit, a key set into said support, said guide member being longitudinally slotted to receive a portion of said key, whereby the guide member is restrained from rotation, said key being covered by and retained in its use position by said adjustable stop element. Y Y i LELANDF; BLATT.

REFERENCES CITED i The following references are of record in the v `le of this patent:

. UNITED STATES PATENTS 'Number Name Date `2,335,614 Spievak Nov. 30, 1943 2,339,324 Fischer Jan. 18, 1944 2,401,490 Little June 4, 1946 2,402,353 Trautmann June 18, 1946 *2,409,377 Miller Oct. 15, 1946 FOREIGN PATENTS Number l country Date 22,542 Denmark Oct. 22,1917 f 510,482 GreatKBritain Aug. 2,1939 

